A variety of hand held computers are available in the art as shown for example in catalogs from firms such as Personal Computer Products, Inc., P.O. Box 190198, Dallas, Tex. 75219-0198. These computers operate from computer chips which provide more than 100 separate built-in programs for performing arithmetic and data processing functions. The chips are rapidly becoming more diverse and the capacity of keyboards to handle more functions in hand held computers is limited.
Keyboard U.S. Pat. No. 3,892,958 - July 1, 1975 to C. C. Tung is exemplary of the trend in keyboards. The objective is to reduce the number of computer keyboard keys and 35 keys are used. Prefix keys (gold - f and blue - g) are used for establishing an execution selection mode to permit the keyboard to select different function modes thereby permitting some keys to serve different purposes. This extends the range of a 39 key keyboard available in a Hewlett Packard Model 15C computer to make accessible more of the built-in operating function and program modes, namely 96, which is undoubtedly far less than the number available on computer chips in the present state of the art. Thus, access to the full capacities of the chips is not feasible with the prior art keyboards, and a relatively large number of keys is still required.
Furthermore, with the 39 keys, as illustrative of the trend to more powerful chips, in a hand held computer the keys have to be placed so close together that it is difficult to make choices manually without fingering a wrong key. Also a sequence of reasoned selections must be made on prior art keyboards that introduces many opportunities for potential error into the key selection process. For example, in the referenced patent, a key must be found with a desired function, the color noted and then a prefix color key actuated on a different part of the keyboard before returning to the selected function. With keys spaced by the order of one centimeter apart and a human finger of the breadth of about two centimeters, there is little room, which breeds errors.
Also, if the technique is adopted for larger keyboards it is very difficult to learn a "touch" selection system because of the large number of keys and awkward finger positions. It would certainly be desirable therefore to confine the keyboard reach to fall more into line with that of the number entry keys conventional in simple calculators used by accountants and the like.
It is therefore a general object of this invention to improve the state of the art in computer keyboards by correction of the foregoing prior art deficiencies. Other objects, features and advantages of the invention will be found throughout the following description and claims and in the accompanying drawing.